English isn't my native language and I'm not sure how to best use contractions in my game. I have decided not to use slang because it would just make it harder for me. I try to stick with the "rules" but in this case I'm not sure what the rules are. I have considered not using any contractions at all but that seems to make dialogs a bit clumsy and not as fluent so I'm pretty sure that I want to use at least some contractions.

Which contractions should I use? I have found many lists but they all contain a different set of contractions.

Is it weird to using some contractions but not others? If I use contractions such as I'm, he's and you're would it be weird not to use he'd, you'll and we've?

How important is it to be consistent? If I use a contraction once should I make sure to use it consistently everywhere?

In which situations should contractions be avoided? I know that contractions are seldom used at the end of sentences (e.g. I'm older than you're). The two words also need to belong together (e.g. the socks that I gave you're blue). Are there more?

Is there a difference in the use of contractions between British English and American English?

You can't contract if it has emphasis on it or is contrasting something (That's what's really happening in I'm older than you are). Anything else is fair game, as long as the 2 words form a phrase (= belong together).

The first thing I'd note is that contractions are never required. If you're unsure, "you are" is fine. At worst, it might make you look foreign, which, well, you are. No particular problem.

But in general, a contraction only works if the two words have no separation between them. That's why your second example fails. "are blue" is a clause referring to "the socks", not to "you". "You" is a part of the description of "the socks". Therefore, contracting "you" and "are" is unacceptable; it makes no sense.

As for contractions at the end of sentences, that's not really true. It's perfectly common for "aren't", "ain't" (when used), "isn't", etc at the end of a sentence. "No it isn't" is a common example. The problem with your first example is more that "you're" should only be used when "are" has relatively no emphasis. Sentences like "You're an American", where "are" is just there because it's grammatically necessary. Other forms of "to be" are the same (e.g. "I'm" and "he's"). No such problem exists for contracting out "not" in any case I'm aware of, and a lot of people (like me) literally contract out "not" every chance they get, with the exception of "ain't" (since that one is seen as crude).

Thank you, both of you. The examples that I gave are extremes. I do feel they are wrong and I would never accidentally write such things. Sometimes contractions come naturally, sometimes I'm not sure, and sometimes I think I can use both so I should probably use the contraction but sometimes the uncontracted version feels better. When I speak English, which I rarely do, I use quite few contractions so I guess that has something to do with it.

What you said about emphasis is interesting but I'm afraid I'm not very good at knowing where the emphasis is in a sentence. Sometimes it's obvious but most of the time it just doesn't seem to matter. I have been told that every sentence has emphasis so does that mean I need to identify the emphasis for every sentence or can I just use the contraction and the emphasis will automatically move to another word?

Let's just use a sentence from what onpon4 wrote as an example.

That's why your second example fails.

I guess the emphasis here is on why. But couldn't it also have been on that's to emphasis that the explanations given by the others were wrong? Does that mean it would have to be rewritten as that is, or is that only necessary if the emphasis is specifically on is?

Since my target audience isn't exclusively native English speakers it might not be so bad if I don't use contractions everywhere, but I think at least some will be necessary to get a little better flow in the language. I haven't got started with any serious writing yet, still got coding I want to do first. It will probably work out just fine but I'm a little bit concerned the language might drift if I don't have a plan, so that more contractions are used at the end of the game when I've become more used to 'em.